LLTO

LLTO, short for lithium lanthanum titanate, is a ceramic oxide solid electrolyte with the chemical formula Li0.5La0.5TiO3. It adopts a perovskite-derived structure in which Li+ and La3+ occupy the A-site of the ABO3 lattice and Ti4+ sits at the B-site, with oxygen forming octahedra around Ti. The partial substitution of Li+ on the A-site creates a high concentration of lithium vacancies that facilitate ionic transport.

Electrical properties: LLTO exhibits relatively high lithium-ion conductivity for a ceramic electrolyte, with bulk conductivities on the order of 10^-3 to 10^-4 S/cm at room temperature and higher values at elevated temperatures. However, grain boundaries in polycrystalline samples contribute substantial resistance, so the overall conductivity is often limited by intergranular blocking. The material shows low electronic conductivity, which is desirable for solid electrolytes.

Stability and challenges: LLTO is sensitive to moisture and can degrade under humid conditions. Its compatibility with lithium metal and other electrode materials at interfaces is a concern, and Li loss at grain boundaries can degrade performance. These issues motivate efforts to modify the microstructure and chemistry to improve stability and interfacial behavior.

Enhancement strategies: Aliovalent doping at the A-site (for example with Nb, Ta, or Al) and processing approaches that improve densification and reduce grain-boundary resistance are common. Researchers also explore composite electrolytes that combine LLTO with other ion conductors to balance conductivity and stability.

Applications and status: LLTO has been widely studied as a solid electrolyte candidate for all-solid-state lithium batteries, particularly in academic research. While it demonstrates favorable bulk ion transport, practical implementation faces challenges related to grain boundaries, stability, and interfacial compatibility, and LLTO remains primarily a research material rather than a commercial electrolyte.